This invention provides improved olefin polymerization catalysts, and method of making them, formed from solid oxides of silicon or aluminum, organomagnesium compounds, and titanium compounds. One type of such catalysts is formed by the interaction of a selected said oxide, an organomagnesium compound, and a titanium halide compound. The improvement is achieved principally by treating the oxide with a compound that contains fluorine.
The invention also provides improved methods of making polymers using the improved catalysts of the invention.
The organomagnesium compound of the catalyst may be a complex of a dialkyl magnesium compound with trialkylaluminum. Consequently, one object of this invention is to improve the catalysts disclosed in Shida et al. patent application Ser. No. 63,111 filed Aug. 1, 1979, and now U.S. Pat. No. 4,263,171 and assigned to the same assignee as is the present application. The fluorine treatment of this invention renders such catalysts more reactive at titanium levels of less than about 6% by weight. Thus, it becomes possible to prepare catalysts of this type with equivalent reactivity but with a decreased titanium content.
Another object of this invention is to provide catalysts for the manufacture of particle form polyethylene of high melt index with improved reactivity and higher melt index by combining the fluorine treatment of the silica with an alcohol modification.
The organomagnesium compound of the catalyst may be an uncomplexed dialkyl magnesium compound, an alkyl or aryl magnesium halide, or an ether complexed Grignard reagent. Consequently, in this respect the scope of this invention is broader than that of the above Sida et al. application invention.
Four prior art patents deal specifically with catalysts made with an organomagnesium compound and silica: U.S. Pat. No. 3,821,186, British Pat. No. 1,484,154, Sept. 1, 1977, U.S. Pat. No. 3,787,384 and U.S. Pat. No. 4,148,754.
The catalysts of this invention may be made in the same manner as those of the above Shida et al. application 63,111 except that the inorganic oxide is first treated with a fluorine compound. Fluorinated supports for olefin polymerization catalysts are described in U.S. Pat. Nos. 3,936,431 and 3,978,031. In U.S. Pat. No. 3,936,431, the support must be a complex oxide having the general formula MgO.Al.sub.2 O.sub.3, and after reaction with the fluorinating agent, the F/Al ratio must be from 0.1 to 0.15. In U.S. Pat. No. 3,978,031, the support must be alumina, which acquires a F/Al ratio of 0.01 to 0.30 by the fluorination reaction. Silica itself is not included in either of these patents.
In addition, neither discloses contacting the fluorinated support with an organomagnesium compound before contact with the titanium compound as in one aspect of this invention. These two patents reveal that organomagnesium compounds may be used in the role of a cocatalyst but in no other way.
U.S. Pat. No. 3,513,150 describes treating gamma-alumina with gaseous titanium tetrachloride, and then a gas containing a chlorinating agent, for the purpose of making an olefin polymerization catalyst.
U.S. Pat. No. 3,888,789 teaches treating a high surface area oxide with a halogenating agent X.sub.2 or RX.sub.n, where X is preferably chlorine or bromine, and R is SO, SO.sub.2 or a hydrocarbon radical.
In U.S. Pat. No. 4,144,390, a magnesium alkoxide or phenoxide is treated with a halogenating agent as a first step in catalyst preparation.